1. Field of the Invention
The present invention relates to synthetic insect attractant compositions. More particularly, the invention relates to chemical attractant compositions and use thereof to detect, survey, monitor, and/or control frugivorous pest insects such as Anastrepha species, more particularly Anastrepha ludens (Loew), Anastrepha suspensa (Loew).
2. Description of the Art
Control of frugivorous pest flies is of considerable economic importance for fruit and vegetable production and export. Quarantine and regulatory agents expend substantial efforts to detect newly introduced species of economically important fruit flies. The Mexican fruit fly, Anastrepha ludens (Loew) is a frugivorous tephritid ranging from southern Texas to at least Costa Rica (Stone, The Fruit flies of the genus Anastrepha, U.S. Department of Agriculture Misc. Publ. 439, 1942). This fly is one of the most polyphagous of the approximately 180 species of the genus Anastrepha, known in the field from at least 36 species of hosts in 14 plant families (Norrbom and Kim, A list of the reported host plants of species of Anastrepha (Diptera:Tephritidae), U.S. Department of Agric. Animal Plant Health Insp. Serv., APHIS 81-52:114 p., 1988). Its affinity for citrus has made it one of the most economically important insects in citrus-growing regions all over the world. This is especially true where it does not occur naturally, but where accidental introduction could cause an economic catastrophe to the citrus industry. Even a small infestation makes all fruit grown in the area suspect and thus unsalable to many would-be importing countries without costly post-harvest treatments or radical extermination programs. Because of this threat, much emphasis has been placed on detection of this species before its populations can become well established and thus difficult to eradicate. The Caribbean fruit fly, Anastrepha suspensa (Loew), is known to infest over 80 species of fruit. The presence of the Caribbean fruit fly in Florida posses a constant threat to other citrus growing regions.
Much emphasis has been placed on detection and eradication of frugivorous pest flies. The development of improved lures is needed to monitor and suppress populations of this and other pest fruit flies and to prevent establishment of populations in areas that are currently without these pests.
Methods developed for monitoring, controlling, and eradicating frugivorous fruit flies (Tephritidae) have relied extensively on the use of chemical attractants. Methyl eugenol plus dibrom; cuelure plus dibrom; ammonium salts; and a mixture of 1,7-dioxasprio[5,5]undecane with .alpha.-pinene or n-nonanal; and spiroacetal are used as lures for species of Dacus. A composition of hexyl acetate, (E)-2-hexen-lyl acetate, butyl 2-methylbutanoate, propyl hexanoate, hexyl propanoate, butyl hexanoate, and hexyl butanoate is used as a lure for species of Rhagoletis. Effective insect-detection systems are essential for preventing the establishment of fruit flies and surveys for these flies are included in state and federal exotic pest-detection programs in at least nine southern and southwestern states (Lance and Gates, J. Econ. Entomol., Volume 87, 1377-1383, 1994). Califormia, Texas, and Florida maintain large number of trimedlure-baited Jackson traps ((Harris et al., J. Econ. Entomol., Volume 64, 62-65, 1971) for the detection of male C. capitata and aqueous protein-baited McPhail traps (Newwll, J. Econ. Entomol., Volume 29, 116-120, 1936; McPhail, J. Econ. Entomol., Volume 32, 758-761, 1939) for detection of male and female C. capitata (Mediterranean fruit fly) and A. ludens (USDA, National exotic fruit fly trapping protocol, Animal and Plant Health Inspection Service, Plant Protection and Quarantine, Hyattsville, Md., 1991). McPhail traps are currently used for monitoring fruit flies throughout fruit growing areas of the world. There are several problems associated with use of either of these trapping systems. Although trimedlure is effective in attracting male Mediterranean fruit flies, it is either only weakly active in attracting or is completely ineffective in attracting female Mediterranean fruit flies (Nakagawa et al., J. of Econ. Entomol., Volume 63, 227-229, 1970). Inability to capture female C. capitata limits the effectiveness of trimedlure-baited traps as a control device and no information on population dynamics of the female flies is obtained. McPhail traps, bell-shaped glass traps with a water reservoir containing aqueous protein baits, offer the advantage of attracting both male and female C. capitata and A. ludens fruit flies. However, these traps are cumbersome and have numerous disadvantages of their own. Servicing the trap requires that water and bait be added in a somewhat maladroit manner in which the trap is turned upside down, bait added and then the trap returned to an upright position. This process often results in bait spillage, and the spilled bait becomes a food source for flies outside the trap. Removal of insects trapped requires considerable effort. The contents of the trap must be filtered through a screen to separate the insects from the bait solution. Trapped fruit flies are often found severely decomposed with parts missing. Thus, when these traps are used in conjunction with marked flies in sterile release programs difficulty is encountered in determining whether a trapped fly is a sterile or a wild fly. Other factors that contribute to the difficulty in the deployment of McPhail traps include the size and weight of the trap, and the fragile nature of glass. Protein baits also attract a number of non-targeted insects and considerable time is required to sort among the trapped insects.
Conventional lures currently used to survey and detect frugivorous pests are protein baits such as fermenting yeast hydrolysate (Greany et al., Ent. exp & Appl. 21:63-70, 1977) and protein hydrosylate (McPhail, J. Econ. Entomol. 32:758-761, 1939). The problem with protein lures is that they capture large numbers of nontarget insects. Furthermore, the only lures that are available for attracting both female and male fruit flies are protein baits.
Adult fruit flies require sugar to survive (Christenson & Foote, Annual Review of Entomology 5:171-192, 1960), and honeydew secreted by homopterous insects is recognized as an important food source for adult tephritids (Christenson et al., Annual Review of Entomology 5:171-192, 1960). Female fruit flies also require protein to ensure fecundity, and this protein requirement is the primary basis for traps for detection of female fruit flies.
Hundreds of compounds are known to be released from protein baits (Morton & Bateman, Aust. J. Agric. Res. 32:905-916, 1981). Examples of some volatile components of commercial hydrolyzed protein insect baits are phenylacetaldehyde, acetic acid, furfuryl alcohol, 2-acetylfuran, benzaldehyde, methanol, 2-acetylpyirole, furfural, 5-methyl-2-phenyl-2-hexenal, 5-methyl-2-[(methylthio)methyl]-2-hexenal and ammonia. Ammonia (Bateman & Morton, Aust. J. Agric. Res. 32:883-903, 1981; Mazor et al., Entomol. Exp. Appl. 43:25-29, 1987), acetic acid (Keiser et al., Lloydia 38: 141-152, 1976), and various other volatiles (Buttery et al., J. Agric. Food Chem. 31: 689-692, 1983) have been investigated as attractants for fruit flies. These reports, however, do not provide information regarding released amounts or ratios of the compounds tested or the effectiveness of these chemicals as compared to McPhail traps.
Bacteria in the family Enterobacteriaceae have been found in association with tephritid fruit flies (e.g., Rubio and McFadden, Annu. Entomolo. Soc. Amer., Volume 59, 1015-1016, 1966; Boush et al., Environ. Entomol., Volume 1, 30-33, 1972; Rossiter et al., In R. Cavallora (ed.), Fruit Flies of Economic Importance, A. A. Balkema, Rotterdam, 77-82, 1982; MacCollom and Rutkowski, In Proceedings, Second International Symposium on Fruit Flies, Crete, Greece, 251-253, 1986; Jang and Nishima, Environ. Entomol., Volume 19, 1726-1731, 1990) and bacteria in this family may be strongly attractive to fruit flies (Drew and Lloyd, In A. S. Robinson and G. Hooper (eds.), World Crop Pests, Volume 3A, Fruit Flies Their Biology, Natural Enemies and Control, Elsevier, N.Y., 131-140, 1989; Martinez et al., Florida Entomol., Volume 77, 117-126, 1994). Bacteria on plant surfaces may serve as a protein source for adult tephritids in nature (Drew et al., Oecologia (Berlin), Volume 60, 279-284, 1983). Drew and Fay (J. Plant Prot. Tropics, Volume 5, 127-130, 1988) hypothesized that increased capture of Bactrocera tryoni (Froggatt) in liquid protein bait with bacteria was due to volatile metabolites produced by bacterial growth. Davis et al. (J. Agric. Entomol., Volume 1, 236-248, 1984) demonstrated that there was greater attraction of Caribbean fruit flies, Anastrepha suspensa (Loew), to liquid protein bait solution in McPhail traps versus liquid protein bait placed on cotton wicks in Jackson traps and speculated that this was due in part to volatile end products from microbial breakdown that occurred in the McPhail traps.
Several studies have evaluated the attractiveness of various bacteria that were found in association with tephritids. Jang and Nishijima (1990, supra) isolated 14 bacterial species from wild and laboratory-reared oriental fruit flies, Batrocera dordalis Hendel, and most of these bacteria belonged to the family Enterobacteriaceae. They found that several bacterial species were more attractive to female than to male flies and that washed cells, that is cells that were separated from the growth media, were more attractive than water or phosphate buffer. Several strains of Staphylococcus aureus were found to be attractive to adults of the Mexican fruit fly, Anastrepha ludens (Loew)(Robacker et al., Annu. Entomol. Soc. Amer., Volume 84, 555-559, 1991). Attraction to bacterial odors was mediated by feeding history of the flies, as response to bacterial odors decreased with increased sugar hunger (Robacker and Garcia, Environ. Entomol., Volume 22, 1367-1374, 1993) and increased with increased protein hunger (Robacker and Moreno, Florida Entomol., Volume 78, 62-69, 1995). Ammonia, which is known to be the primary fruit fly attractant that is emitted from liquid protein baits (Bateman and Morton, Australian J. Agric. Res., Volume 32, 883-903, 1981; Mazor et al, Entomol.Exp. Appl., Volume 43, 25-29, 1987), is produced by microbial growth (e.g., Howell et al., Phytopathol., Volume 78, 1075-1078, 1988; Scrapati et al, J. Chem. Ecol., Volume 22, 1027-1036, 1996). Several volatile chemicals have been identified from headspace analysis of bacteria and/or culture media (Robacker et al., J. Chem. Ecol., Volume 19, 543-557, 1993; Lee et al., J. Agric. Food Chem., Volume 43, 1348-1351, 1995; DeMilo et al., J. Agric. Food Chem., Volume 44, 607-612, 1996), although Robacker and Flath (J. Chem. Ecol., Volume 21, 1861-1874, 1995) could not determine if the chemicals that were biologically active in laboratory bioassays were produced by the bacteria or were an artifact of the analytical procedure. 3-Methyl-1-butanol has been identified previously from fruit fly attractive substances. It was one of 28 chemicals identified as volatiles emitted from fermented host fruit for A. ludens (Robacker et al, J. Chem. Ecol., Volume 16, 2799-2815, 1990). It was not attractive by itself, and it was removed from further consideration as a host fruit attractant volatile. Research of volatiles from bacteria indicated that 3-methyl-1-butanol was the major volatile obtained from autoclaved supernatant of 8-day old cultures of Klebsiella pneumoniae-inoculated TSB (Lee et al, 1995, supra) and of 4- and 8-day old cultures of Citrobacter freundii-inoculated TSB (DeMilo et al, 1996, supra). There were 20 and 21 chemical components, respectively, identified in addition to this compound. However, there was no information regarding the attractiveness of the individual chemicals. In comparisons of autoclaved supernatant to non-autoclaved supernatant of 4-day old C. freundii-inoculated TSB, the amount of 3-methyl-1-butanol was greatly reduced in the autoclaved supernatant with no corresponding change in A. ludens attraction in laboratory bioassays (DeMilo et al., 1996, supra). 3-Methyl-1-butanol was identified as a minor component in vacuum steam distillation extraction of corn protein hydrolyzate bait (Buttery et al., J. Agric. Food Chem., Volume 31, 689-692, 1983). Thus, it is not known if there are volatile chemicals in addition to ammonia produced by actively growing bacteria that are attractive to fruit flies.
Enterobacter agglomerans is one of several Enterobacteriaceae that have been isolated from adults of the apple maggot, Rhagoletis pomonella (Walsh), and from apple maggot-infested fruit (MacCollom et al, J. Econ. Entomol., Volume 85, 83-87, 1992). Washed cell preparations of an apple maggot-associated isolate of E. agglomerans were attractive to foraging adults in field trails while washed cells of Klebsiella ozytoca, Enterobacter cloacae, Psuedomonas fluorescens, and Bacillus cereus captured less flies than E. agglomeran cells (MacCollom et al., 1992, supra). Recently, Lauzon et al. (Environ. Entomol., Volume 27 (4), 853-857,1998) demonstrated that culture plates inoculated with E. agglomerans are attractive to apple maggot flies in laboratory bioassays. However, variation in fruit fly attraction may occur within species as Lauzon et al. found E. agglomerans isolates from different sources varied in ability to attract apple maggot flies and that attraction may be related to the substrates which the isolates are growing (Lauzon et al., J. Chem. Ecol., 1998(b), in press). This bacterium has been isolated from adults, larvae and fruit infested with larvae of the Caribbean fruit fly, Anastrepha suspensa (Loew), field collected in south Florida (C. R. L., unpublished data). While various attractant compositions are known in the art, there remains a need in the art for highly effective attractant compositions to improve monitoring and controlling of frugivorous pest insects, especially those of the genus Anastrepha. The present invention provides a composition and method of use which is different from related art attractant compositions.